Differences in urine levels between active renal versus active extrarenal SLE only were most pronounced for S100A4 level (median [IQR] 8.35 ng/ml [1.7–19.4] in active LN versus 0.63 ng/ml [0.3–1.9] in active extrarenal SLE only; p < 0.0001) (Fig. 3a). The gene discussed is S100A4; the disease is systemic lupus erythematosus.